Trachylepis boehmei, Koppetsch, 2020

Koppetsch, Thore, 2020, A new species of Trachylepis (Squamata: Scincidae) from the Amhara Region Ethiopia, and a key to the Ethiopian Trachylepis, Zootaxa 4859 (1), pp. 113-126 : 115-122

Trachylepis boehmei , sp. nov.

Suggested common English name: Böhme’s Grass Skink urn:lsid:zoobank.org:act:D0E725F7-C9BB-4B6D-929E-386974A67671

Material examined: Holotype: ZFMK 16795 , adult female, Ankober (9°36′N, 39°44′E), elevation 2,450 m.a.sl., North Shewa , Amhara Region, Ethiopia ( Fig. 2 ), collected by G. Nikolaus on 12 November 1975 ( Fig. 1 ).

Paratypes: ZFMK 16785–86 , 16788 , 16791–92 , 16794 and 16796: adult females , ZFMK 16787 , 16789–90 and 16793: adult males, all with the same data as the holotype ( Fig. 4B ) .

Diagnosis: Trachylepis boehmei sp. nov. can be distinguished from all other congeners by the following combination of characters: (1) slender body of small size, SVL up to 55.3 mm; (2) relatively short tail length, up to 69.6 mm (about 1.3 times SVL); (3) relatively short eye–snout distance, up to 0.3 times head length; (4) 26–29 scale rows around midbody; (5) smooth uncarinated dorsal scales; (6) unique colour pattern showing a striped throat (11–12 stripes), a lateral white stripe from eye to tail, dorsally a pale brownish colouration with 6–8 darkish brown stripes ranging from neck to the end of the tail, an unpatterned cremish white ventral colouration and a head with small brown spots dorsally.

Description of the holotype: A small skink with a total length of 103.1 mm (snout-vent length of 46.3 mm and a tail length of 56.8 mm) ( Fig. 1 ). Cylindrical body and slender appearance; habitus and proportions of limbs and body comparable to T. megalura . Complete, non-regenerated tail relatively short, only 1.23 times SVL. Compact head (HL 9.8 mm; HW 6.2 mm) with blunt snout (ESD/HL 0.24) ( Fig. 1D,E,F ). Small, vertically oval ear opening. Transparent scale characteristic for Trachylepis skinks present in lower eyelid. Small nostrils, set posteriorly so that postnasal effectively borders the nostril. Rostral visible from above. Supranasals with contact. Wide frontonasal, in contact with loreal scale. Prefrontals in contact with each other, also bordering frontal, frontonasal, loreal, first and second supraocular and first supraciliary. Two loreals. Frontoparietals in contact with each other, also bordering frontal, third and fourth supraoculars, parietal and interparietal. Parietals only in slight contact. Frontal in contact with two supraoculars on each side. Frontoparietal plus interparietal length greater than frontal length. Interparietal with a visible parietal foramen. Five supraciliaries, seven supralabials. Both dorsal and ventral scales smooth without being even slightly keeled or carinated. 26 scales around midbody (MSR), 57 paravertebral scale rows (PSR). The limbs have five digits, order of finger size (first longest) is IV>III>II>V>I, relative length of toes IV>III>V>II>I. Smooth tarsal and palmar scalation. 13 subdigital lamellae under fourth finger, 16 subdigital lamellae under fourth toe.

Additional mensural and meristic measurements of the holotype are shown in Table 1 .

Colour pattern in preservative: The female holotype shows a striped throat with twelve stripes ( Fig. 1D ). A lateral white stripe extends from the eye to the tail. Dorsally the holotype is coloured pale brownish with six darkish brown stripes ranging from the neck to the end of the tail ( Fig. 1C ). Posteriorly those stripes are discontinuous by flowing into each other. On the ventral side it shows an unpatterned cremish white colouration ( Fig. 1A ). On the dorsal side of the head small brown spots are present ( Fig. 1F ).

Variation: Variation in mensural and meristic characters for the adult type series is shown in Table 1 . The paratypes of Trachylepis boehmei sp. nov. show eleven to twelve ventral stripes on the throat. Six to eight darkish brown stripes range from neck to the end of the tail. Head scalation is similar to holotype except for the contact of parietals and the contact of prefrontals, which vary in the paratypes from being separated to bordering each other ( Fig. 4B ).

Comparisons: Trachylepis boehmei sp. nov. can be easily distinguished from the other representatives of the genus Trachylepis occurring in Ethiopia (see the key to the Ethiopian Trachylepis provided below) by a variety of morphological characteristics. By having a smooth dorsal scalation it can be separated from all congeners showing a characteristic number of distinct keels (indicated in brackets) on their dorsal scales, T. brevicollis (2–3), T. hildebrandtii (3), T. maculilabris (5–8), T. planifrons (3, rarely 4–5), T. quinquetaeniata (3, rarely 4–5), T. striata (3, rarely up to 7), T. varia (3) and T. wingati (3). In addition, Trachylepis boehmei sp. nov. shows a comparable low number of midbody scale rows (26–29) and is easily distinguishable from T. brevicollis (30–35), T. hildebrandtii (32), T. maculilabris (30–38, rarely more than 34), T. quinquetaeniata (32–46, rarely more than 40), T. striata (32–42, rarely more than 36) and T. wingati (30–32). It differs from T. megalura by having a relatively short tail length, maximal 1.7 times the SVL (vs. generally more than twice the SVL), a relatively low eye–snout distance, up to 0.3 times the head length (vs. 0.4) and a shorter body size of around 46.8 mm SVL (vs. generally more than 55 mm SVL). Most specimens of T. megalura show at least 3 indistinct keels on their dorsal scales (vs. completely absent in the new species) ( Marques et al., 2019), but in some populations these can be also completely reduced (T. Mazuch, pers. commun.). Although, Trachylepis boehmei sp. nov. shows the closest morphological resemblance concerning its habitus and appearance to T. megalura , it is additionally distinguishable by its coloration and number of midbody scale rows. Both species have a prominent lateral white band running from below the eye along the entire body to the tail. However, T. megalura shows only 4 darkish brown, relatively indistinct fine dorsal stripes from the neck to the base of the tail, while the new species differs in having 6–8 darkish brown stripes dorsally ranging from the neck to the end of the tail by flowing into each other. While a maximum range of 22–28 scale rows at midbody has been reported for T. megalura , most individuals show 24–26 MSR, a lower number compared to Trachylepis boehmei sp. nov. having 26–29 MSR.

Despite the fact that the type series has been assigned to T. irregularis before, this biogeographically separated montane endemic from Kenya and Uganda can be easily distinguished from the new species by having 2–5 (regularly 3–4) distinct dorsal keels and a prominent vertebral whitish or golden double-stripe and two dorsolateral white stripes (see figure 2 in Koppetsch , in prep) .

Comparisons are based on species characteristics from Largen & Spawls (2010), Sindaco et al. (2012) and Marques et al. (2019). Differences between Trachylepis boehmei sp. nov. and congeners of similar habitus and size are shown in Table 2 .

Etymology: The species is named after Wolfgang Böhme, German herpetologist at the Zoological Research Museum Alexander Koenig in Bonn, to honour his comprehensive and passionate research on African herpetofauna, the numerous contributions to its knowledge and his outstanding and ongoing strong promotion and supervision of the author.

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Distribution, conservation and natural history: At present, Trachylepis boehmei sp. nov. is only known from its type locality, at elevations more than 2,400 m.a.sl. around Ankober in Ethiopia ( Fig. 2 ). It is likely that this species also inhabits parts of the Ethiopian Highlands near the type locality in the eastern Amhara region, in particular other surrounding mountain ranges of higher altitude west of the Great Rift. While no observations of living specimens have been made so far, it is likely that also this newly described species of Trachylepis shows a diurnal activity pattern and lives predominantly on the ground or lower vegetation of mountainous moor- or moist grasslands at medium or higher elevation ( Largen & Spawls, 2010), similar to other representatives of the T. varia group sensu Weinell et al. (2019), particularly to T. megalura . The currently known distribution range of Trachylepis boehmei sp. nov. is only restricted to a small area outside protected areas or a national park. Therefore, habitat destruction and fragmentation resulting from expansions of agricultural areas or logging activities might threaten this possibly endemic species and its ecological requirements. Nevertheless, its occurrence in the Wof-Washa Forest located between the Ankober, Tarmaber, and Basona Worana districts cannot be ruled out.

Six of the seven of the female paratypes, whose reproductive tracts have been dissected, contained three to four fetuses. Consequently, also Trachylepis boehmei sp. nov. is ovoviviparous, as the other species of the T. varia group ( Weinell et al., 2019). The fetuses revealed by dissection are at different levels of development, but in all of them the ground colour is cremish brown. Like the adults they show a lateral white stripe and six darkish brown stripes ranging from the neck to the end of the tail ( Fig. 4A ). Unlike T. raymondlaurenti , closely related to T. megalura and having neonates with prominent reddish-orange caudal colouration ( Marques et al., 2019), juveniles of Trachylepis boehmei sp. nov. seem to have no brightly coloured tails.

Figures

FIGURE 1. The preserved adult female holotype of Trachylepis boehmei sp. nov. (ZFMK 16795) from Ankober, Ethiopia, in ventral (A), lateral (B) and dorsal view (C). Head in in ventral (D), lateral (E) and dorsal view (F).

FIGURE 2. Map indicating the currently known distribution (red star) of Trachylepis boehmei sp. nov. in Ankober, Ethiopia. Grey dots show records of T. megalura based on distributional data after Marques et al., 2019. The grey dot with a black asterisk indicates the record of the T. megalura specimen from Kafa Biosphere Reserve misidentified as T. wingati in Kirschey (2017).

FIGURE 4. Fetus of Trachylepis boehmei sp. nov. (A) revealed by dissection of the female paratype (ZFMK 16796) (B).